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Home , Heterostachys, Phylloglossum, Selaginella, Selaginella apoda, Selaginella denticulata, Selaginella kraussiana

RESEARCH ARTICLE

AMERICAN JOURNAL OF

A subgeneric classifi cation of (Selaginellaceae)1

Stina Weststrand and Petra Korall 2

PREMISE OF THE STUDY: The family Selaginellaceae includes approximately 750 herbaceous species worldwide, with the main species richness in the tropics and subtropics. We recently presented a phylogenetic analysis of Selaginellaceae based on DNA sequence data and, with the phylogeny as a framework, the study discussed the character evolution of the group focusing on gross morphology. Here we translate these fi ndings into a new classifi cation.

METHODS: To present a robust and useful classifi cation, we identifi ed well-supported monophyletic groups from our previous phylogenetic analysis of 223 species, which together represent the diversity of the family with respect to morphology, , and geographical distribution. Care was taken to choose groups with supporting morphology.

KEY RESULTS: In this classifi cation, we recognize a single Selaginella and seven subgenera: Selaginella , Rupestrae , Lepidophyllae , Gymnogynum , Exal- tatae , Ericetorum , and Stachygynandrum . The subgenera are all well supported based on analysis of DNA sequence data and morphology. A key to the subgenera is presented.

CONCLUSIONS: Our new classifi cation is based on a well-founded hypothesis of the evolutionary relationships of Selaginella, and each subgenus can be identifi ed by a suite of morphological features, most of them possible to study in the fi eld. Our intention is that the classifi cation will be useful not only to experts in the fi eld, but also to a broader audience.

KEY WORDS classifi cation; key; ; morphology; phylogeny; Selaginellaceae; subgenera

Th e phylogeny of Selaginellaceae Willk., one of three lycophyte Jermy, 1986), divided the species into two to several genera (e.g., families, was addressed in a companion article in this issue Palisot de Beauvois, 1804; Rothmaler, 1944; Soják, 1993; Tzvelev, ( Weststrand and Korall, 2016 ) and has been the subject of much 2004 ), or even included all species as subgenera under attention in the last 15 years (e.g., Korall et al., 1999 ; Korall and L. ( Reichenbach, 1828 ), see Zhou and Zhang (2015) for a historical Kenrick, 2002 , 2004 ; Arrigo et al., 2013 ; Zhou et al., 2015c ). In that review. Th e classifi cation most oft en referred to during the last de- large-scale study, we analyzed plastid and single-copy nuclear cades is the one published by Jermy (1986). He recognized a single data from approximately one-third of the 750 species ( Jermy, genus Selaginella with fi ve subgenera: Selaginella (2 species), 1990) and discussed the morphological evolution of the group. Tetragonostachys Jermy (ca. 50 species), Ericetorum Jermy (3 spe- Here we present a new classifi cation of Selaginellaceae, based on cies), Heterostachys Baker (ca. 60 species), and Stachygynandrum these results. (P.Beauv. ex Mirb.) Baker (ca. 600 species). Morphological features Th e genus Selaginella was fi rst described by Palisot de Beauvois used to distinguish groups in classifi cations were, e.g., isophylly vs. in 1804 . Since then, a number of classifi cations have been proposed anisophylly, phyllotaxy, habit, stelar arrangement, and orna- that either recognized a single genus Selaginella P.Beauv. (e.g., mentation. Phylogenetic studies of the group have shown that these Spring, 1840 , 1849 ; Braun, 1858 ; Baker, 1883 ; Hieronymus and characters (as they have been defi ned) oft en are homoplastic, in- Sadebeck, 1901 ; Walton and Alston, 1938 ; Tryon and Tryon, 1982 ; volving reversals and/or parallelisms, and that none of these mor- phology-based classifi cations properly refl ect the phylogeny of the 1 Manuscript received 8 April 2016; revision accepted 30 September 2016. group ( Korall and Kenrick, 2002 ; Zhou et al., 2015c ; Weststrand Systematic Biology, Department of Organismal Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden and Korall, 2016 ). In 2015, Zhou and Zhang published the fi rst clas- 2 Author for correspondence (e-mail: [email protected]) sifi cation based on a phylogenetic analysis of the group ( Zhou et al., doi:10.3732/ajb.1600288 2015c ). On the basis of this study, in combination with morphological

2160 • AMERICAN JOURNAL OF BOTANY 103 (12): 2160 – 2169 , 2016; http://www.amjbot.org/ © 2016 Weststrand and Korall. Published by the Botanical Society of America. This work is licensed under a Creative Commons Attribution License (CC-BY 4.0). DECEMBER 2016 , VOLUME 103 • WESTSTRAND AND KORALL—SUBGENERIC CLASSIFICATION OF SELAGINELLA • 2161

and chromosome data ( Zhou et al., 2015c ), Zhou and Zhang (2015) 1901 ; Steel, 1923 ). However, rhizophore development is complex recognized six subgenera and 18 sections within the single genus and variable, and this division into rhizophore positions does not Selaginella . fully refl ect the variation observed. More comparative studies are Selaginellaceae, with the single genus Selaginella , is widely dis- needed for a full understanding (but see, e.g., Webster and Steeves, tributed throughout the world, from arctic and alpine regions to 1964 ; Lu and Jernstedt, 1996; and references therein). Th e stems of the tropics and subtropics, where the main species diversity is some species have articulations below stem dichotomies; these are found ( Jermy, 1990 ). Th e species are herbaceous and range from swellings that in dried specimens oft en are seen as dark constricted creeping, sometimes mat-forming, to erect, and occasionally long segments ( Jermy, 1990 ). Th e stem stele is a protostele, which in and scandent. Approximately 50 species, most of them found in most species is a simple, circular to elliptic monostele, but bistelic, temperate and dry areas of the world, have vegetative that are tristelic, or polystelic arrangements are also relatively common monomorphic ( Jermy, 1990 ). Th ese have helically arranged leaves, (e.g., Harvey-Gibson, 1894 ; Hieronymus and Sadebeck, 1901 ). except for three species where the leaves are decussately arranged Lobed protostelic forms (actinostele or actino-plectostele) are [ Selaginella gracillima (Kunze) Spring ex Salomon, S. pygmaea found in a few species (e.g., Wardlaw, 1925 ; Mickel and Hellwig, (Kaulf.) Alston, and S. uliginosa (Labill.) Spring] ( Jermy, 1986 ). 1969 ; Weststrand and Korall, 2016 ). A few species also have a sole- However, the majority of Selaginella species, most of them found in nostelic rhizome (e.g., Harvey-Gibson, 1894 ; Steel, 1923 ). warm and humid regions, have dimorphic vegetative leaves. Th e Our knowledge of the phylogenetic relationships of Selaginella- anisophyllous shoots have leaves in four rows with two rows of ceae has increased signifi cantly since the fi rst phylogenetic analysis smaller leaves on the upper, dorsal side of the shoot, and two rows was published in 1999 (Korall et al., 1999). Our study in this issue of larger leaves on the lower, ventral side (Jermy, 1990; see fi g. 3 of ( Weststrand and Korall, 2016 ) showed, based on 223 species, an Korall and Kenrick, 2002 ). overall well-resolved and well-supported phylogeny. Th e resulting Selaginellaceae is heterosporous, a synapomorphy shared with topology is in concordance with previously published phylogenetic the sister lineage Isoëtaceae Dumort. ( Jermy, 1990 ; Wikström and analyses of the group (Korall et al., 1999; Korall and Kenrick, 2002, Kenrick, 1997 ; Korall et al., 1999 ). Th e mega- and microsporangia, 2004 ; Arrigo et al., 2013; Zhou et al., 2015c). Together, the diff erent enclosing mega- and , respectively, are subtended by studies show that Selaginellaceae is supported as monophyletic and and arranged in strobili at branch tips (Jermy, 1990; with that a clade of two species (the isophyllous S. selaginoides and S. a few exceptions, see, e.g., Valdespino et al., 2015). Th e strobili are, defl exa) is sister to the rhizophoric clade, including all other taxa like the vegetative shoots, either isophyllous or anisophyllous. Iso- (Fig. 1) . Th e rhizophoric clade is supported by two morphological phyllous strobili are most common and found in all species with iso- synapomorphies: presence of rhizophores and tetrastichous stro- phyllous vegetative shoots, as well as in the majority of species with bili. Th e fi rst divergence in the rhizophoric clade gives rise to clades anisophyllous vegetative shoots (Jermy, 1990). Th e sporophylls are in A and B. Clade B and fi ve major subclades within clade A can each tetrastichous strobili in all but two species, the type S. selaginoides be identifi ed based on a suite of morphological features ( Weststrand (L.) P.Beauv. ex Schrank & Mart. and S. defl exa Brack., where they and Korall, 2016 ). are helically arranged (Jermy, 1986). Approximately 60 species have Based on our molecular and morphological work (Weststrand bilateral strobili ( Jermy, 1990 ). A few of these have smaller sporo- and Korall, 2016 ), we here propose a revised subgeneric classifi ca- phylls arranged in the same plane as smaller vegetative leaves, a so- tion of Selaginella refl ecting our current knowledge of the evolu- called nonresupinate , but most species have resupinate tionary relationships of the group. For the classifi cation to be useful strobili, with smaller sporophylls in the same plane as larger vegeta- for future work on Selaginella with respect to research and curation tive leaves (Quansah and Th omas, 1985). Th is hetero- in herbaria, as well as to the general public, we considered the fol- morphism does not refer to the size diff erences sometimes observed lowing criteria to be of importance: (1) stability—the groups named between mega- and microsporophylls. Th e arrangement of mega- should be monophyletic and well supported by phylogenetic analy- and microsporangia in strobili diff ers among and within species ses, that is, not expected to change in the near future, (2) morpho- (Horner and Arnott, 1963; Quansah, 1988). Th e presence of a single logical identifi cation—the subgenera should, as far as possible, basal megasporangium in an otherwise microsporangiate strobilus be recognizable by (gross) morphological features that are easily is, however, almost always consistent within species ( Quansah, studied, and (3) a conservative approach—unless the evidence is 1988). morphology and anatomy have been studied ex- convincing, we prefer to deviate as little as possible from Jermy’s tensively in Selaginella (see, e.g., Minaki, 1984 ; Morbelli et al., 2001 ; (1986) well-established classifi cation, and the historical recognition Korall and Taylor, 2006; Zhou et al., 2015b). Megaspore surface or- of morphologically well-founded groups (i.e., series Articulatae namentation ranges from almost smooth to solitary protrusions or (Spring) Hieron. & Sadeb.). intricate reticulate structures. Cross sections of the exospore show As in many previous classifi cations (e.g., Spring, 1840, 1849 ; complex structures where a very ordered grid-like exospore wall is Baker, 1883; Hieronymus and Sadebeck, 1901; Walton and Alston, most conspicuous (Korall and Taylor, 2006). Th e evolutionary his- 1938 ; Tryon and Tryon, 1982 ; Jermy, 1986 ; Soják, 1993 ; Zhou and tory of both megaspore surface and cross section patterns is compli- Zhang, 2015 ), we treat Selaginellaceae as a monotypic family with cated, involving parallelisms and reversals ( Weststrand and Korall, the single genus Selaginella . Th e type of the genus is Selaginella se- 2016 , in this issue). laginoides, which means that, based on the phylogenetic relation- All but two species (S. selaginoides and S. defl exa) have rhizo- ships found, any division into several genera would lead to the phores, -like organs arising along the stems ( Karrfalt, 1981 ; genus Selaginella including only two species: S. selaginoides and S. Jermy, 1990 ; Schulz et al., 2010 ; and references therein). Th e rhizo- defl exa . All other species, nearly all described and known in fl oras phores mostly emerge from the ventral or dorsal sides in branch under the well-established generic name Selaginella , would have to dichotomies of aerial shoots, but sometimes also from creeping rhi- be transferred to other genera. Besides the large number of recom- zomes (see, e.g., Harvey-Gibson, 1894; Hieronymus and Sadebeck, binations needed, we see two major problems with such a scenario. 2162 • AMERICAN JOURNAL OF BOTANY

We propose a division of Selaginella into seven subgenera. Our study, as well as previous studies ( Korall et al., 1999 ; Korall and Kenrick, 2002 , 2004 ; Arrigo et al., 2013 ; Zhou et al., 2015c ; Weststrand and Korall, 2016), have shown that three of Jermy’s (1986) fi ve sub- genera are nonmonophyletic, leaving only two (subg. Selaginella and subg. Tetragonostachys Jermy), as monophyletic with strong support. Th ese two groups are retained at subgeneric rank in our classifi ca- tion, but the name for subg. Tetragonostachys , needs to be replaced. Zhou and Zhang (2015) considered the epithet to be “confusingly similar” to Lycopodium [unranked] Tetragonostachya Hook. & Grev. [= Selaginella [unranked] Tetragonostachyae (Hook. & Grev.) Spring] and therefore treated them as homonyms under Art. 53.4 ( McNeill et al., 2012). We therefore call this group subg. Rupestrae Weststrand & Korall subg. nov., the epithet being a plural adjective based on the name of the type of the subgenus. For subg. Ericetorum Jermy and subg. Stachygynandrum (P.Beauv. ex Mirb.) Baker the circumscrip- tions are altered to represent monophyletic groups. Th ree additional subgenera are described: Exaltatae Weststrand & Korall subg. nov., Lepidophyllae (Li Bing Zhang & X.M.Zhou) Weststrand & Korall stat. nov., and Gymnogynum (P.Beauv.) Weststrand & Korall comb. nov. Th e fi rst two epithets are based on the names of the type of each subgenus, as for subg. Rupestrae , above. For the species that will now be included in subg. Gymnogynum , the epithet Articulatae has oft en been used. Articulatae was introduced by Spring in 1840 and has since then been used in many classifi cations at ranks below subgenus, as well as an informal name of the group. However, at subgeneric level Gymnogynum has priority; it was fi rst introduced by Palisot de Beauvois (1804) at the generic level and later at the subgeneric level by Reichenbach (1828 , under Lycopodium ). We here choose to present a new classifi cation, despite the re- cently published one by Zhou and Zhang (2015 ; based on the phy- logeny presented by Zhou et al. (2015c)). Our main concern with the Zhou and Zhang (2015) classifi cation is that it does not provide unequivocal morphological diagnostic features (including chromo- some data) that separate the subgenera. (Note that table 2 of Zhou and Zhang (2015) does not show the full morphological variation in the characters listed for the subgenera, and their text and key also need to be referred to.) Furthermore, our data ( Weststrand and Korall, 2016 ) show an even more complex picture, both with re- spect to taxon sampling and morphological characters. Th e sub- genera Heterostachys and Stachygynandrum sensu Zhou and Zhang (2015) represent one example of unclear morphological boundar- FIGURE 1 A schematic overview of the phylogenetic relationships of Se- ies. Both subgenera (sensu Zhou and Zhang, 2015) include species laginella depicting the seven subgenera, as well as the three major with dimorphic vegetative leaves in four rows and rhizophores in a clades; the rhizophoric clade, clade A, and clade B (see text for a discus- ventral position. Both also include species with either mono- or di- sion). The phylogeny is taken from Figs. 1 and 2 of Weststrand and Korall morphic sporophylls. In their study, megaspore surface sculpture is (2016), where it was retrieved by Bayesian inference analysis of a com- highlighted as a distinguishing feature, with subg. Heterostachys bined plastid/nuclear three-region data set (rbcL , pgiC , and SQD1 ). All having with mostly solitary protrusions of diff erent nodes shown are supported by a Bayesian posterior probability (PP) of sorts and density, whereas subg. Stachygynandrum has reticulate 1.0, except for clade B (PP 0.97). Clade size is based on number of species, megaspore surfaces ( Zhou and Zhang, 2015 ). Th e reticulate sculp- scaled logarithmically. turing seen also in a few megaspores of subg. Heterostachys (sensu Zhou and Zhang, 2015 ) are referred to as “completely diff erent First, species-level taxonomy, including species delimitations and from the reticulate ornamentations in Selaginella subg. Stachygyn- species numbers, is for many parts of the world unclear, as is the andrum” (Zhou and Zhang, 2015, p. 1134). However, we found no nomenclature. Second, a one-genus approach allows for an unam- fundamental diff erences between the megaspore sculpturing of cer- biguous assignment to genus, both in the fi eld and by nonspecialists, tain species, e.g., S. albociliata P.S.Wang (in their subg. Heter- whereas with a multigenera approach, more in-depth knowledge ostachys ; megaspore description of Zhou et al. (2015b) ) and S. on distinguishing features will be required. Given the latter sce- simplex Baker (in their subg. Stachygynandrum ; megaspore de- nario, misidentifi cations at the generic level will very likely increase, scription of Korall and Taylor (2006)). Another example of prob- leading to inaccurate placement in herbaria. lematic subgeneric delimitation is the distinction between subg. DECEMBER 2016 , VOLUME 103 • WESTSTRAND AND KORALL—SUBGENERIC CLASSIFICATION OF SELAGINELLA • 2163

Pulviniella Li Bing Zhang & X.M.Zhou and subgenera Stachygyn- observations made on voucher material were combined with studies andrum and Heterostachys (sensu Zhou and Zhang, 2015 ). Species of additional herbarium material, when available, as well as litera- in subg. Pulviniella are in gross morphology and growth form very ture data (e.g., Baker, 1885; Harvey-Gibson, 1894; Hieronymus and similar to species in these two other subgenera. Th e megaspores Sadebeck, 1901; Bower, 1908; van Alderwerelt van Rosenburgh, show sculpturing closely similar to those of species referred to as 1915 ; Brause, 1921; Steel, 1923; Wardlaw, 1925; Alston, 1934; Tryon, subg. Heterostachys . In conclusion, we believe that species are dif- 1949 ; Horner and Arnott, 1963 ; Hellwig, 1969 ; Mickel and Hellwig, fi cult to unequivocally assign to a specifi c subgenus based on mor- 1969 ; Crabbe and Jermy, 1973 ; Alston et al., 1981 ; Mukhopadhyay phology using the classifi cation by Zhou and Zhang (2015) . and Sen, 1981 ; Tryon and Tryon, 1982 ; Minaki, 1984 ; Quansah and We see three other main aspects of the classifi cation by Zhou and Th omas, 1985; Dahlen, 1988; Quansah, 1988; Taylor, 1989; Rauh and Zhang (2015) as problematic. First, the name Selaginella subg. Erice- Hagemann, 1991; Tryon and Lugardon, 1991; Valdespino, 1993; torum as used by Zhou and Zhang (2015) is incorrect, since the epi- Gardner, 1997; Stefanović et al., 1997; Jermy and Holmes, 1998; thet Gymnogynum has priority. In 1828, Reichenbach published a Morbelli and Rowley, 1999; Moran and Smith, 2001; Morbelli et al., classifi cation where he recognized Gymnogynum and fi ve other 2001 ; Korall and Kenrick, 2002 ; Liu et al., 2002 ; Mickel et al., 2004 ; groups at the subgeneric level under Lycopodium , citing Palisot de Korall and Taylor, 2006; Roux, 2008; Al-Shehri and Lashin, 2009; Beauvois (“P. B.”) as author of the names. Palisot de Beauvois (1804) Roy and Borthakur, 2011; Maideen et al., 2013; Schulz et al., used these names at the generic level in his classifi cation from 1804 2013 ; Zhang et al., 2013 ; Singh et al., 2014a , b ; Zhou and Zhang, (see also Brizicky (1969) for a discussion of the rank of Reichenbach’s 2015 ; Zhou et al., 2015a – c ). Morphological characters studied were: names). Second, in the phylogeny on which Zhou and Zhang (2015) isophylly vs. anisophylly and phyllotaxy, with respect both to vege- based their classifi cation (Zhou et al., 2015c), a group of species was tative leaves and sporophylls, presence/absence of articulations, intentionally left out due to analytical problems, i.e., S. sinensis rhizophore position, stelar arrangement, and megaspore features. (Desv.) Spring and close allies, that we refer to as the sinensis group Many of these features were used as diagnostic characters in earlier ( Weststrand and Korall, 2016 ). Th is clade is thus not present in their classifications of Selaginella (e.g., Palisot de Beauvois, 1804; classifi cation. Th ird, S. fi ssidentoides (Hook. & Grev.) Spring, the type Reichenbach, 1828 ; Spring, 1840 , 1849 ; Baker, 1883 ; Hieronymus of section Oligomacrosporangiatae Hieron. & Sadeb., was not in- and Sadebeck, 1901; Walton and Alston, 1938; Rothmaler, 1944; cluded in the phylogenetic analysis by Zhou et al. (2015c) . Based on Tryon and Tryon, 1982; Jermy, 1986; Soják, 1993; Tzvelev, 2004; our results (Weststrand and Korall, 2016), S. fi ssidentoides is not Zhou and Zhang, 2015 ). closely related to the species in the section as it is circumscribed by Zhou and Zhang (2015) . Instead, we show strong support for placing S. fi ssidentoides in the sinensis group (i.e., the group not included in RESULTS the classifi cation by Zhou and Zhang [2015] ); it is thus in a distant position in the phylogeny. Zhou and Zhang (2015 , p. 1135) justifi ed In this classifi cation, seven subgenera are recognized ( Fig. 1 ) based on the assumed phylogenetic position of S. fi ssidentoides on morpho- the seven major, well-supported clades that we identifi ed in our phylo- logical grounds: “Based on its monomorphic sporophylls and creep- genetic analysis of Selaginella in this issue (see Fig. 2 of Weststrand and ing stems, it should belong here. Members of this section are very Korall (2016)). Each subgenus is uniquely recognized by a suite of variable (chromosome number, habit, habitat, number of steles, spo- morphological character states ( Table 1 ; Weststrand and Korall, 2016 ). rophylls, and megaspore and morphology).” However, Based on these characters, a key to the subgenera is presented below. as far as we know, none of the other species in sect. Oligomacrospo- A comparison with two recent classifi cations is found in Table 2 . rangiatae as circumscribed by Zhou and Zhang (2015) have few megasporangia, which was a defi ning feature when the name was introduced by Hieronymus and Sadebeck (1901) . In conclusion, the TAXONOMIC TREATMENT usage of the name Selaginella subg. Ericetorum in the classifi cation by Zhou and Zhang (2015) is incorrect given their circumscription, the Selaginella P.Beauv., Mag. Encycl. 9(5): 478 (1804), nom. cons. – classifi cation includes a nonmonophyletic group, Selaginella sect. Selaginoides Ség., Pl. Veron. 3: 51 (1754), nom. rej. – Mirmau Ad- Oligomacrosporangiatae , and excludes S. sinensis and closely related ans., Fam. Pl. 2: 491 (1763), nom. superfl . – Polycocca Hill, Gener. species. Nat. Hist., ed. 2, 2 (Hist. Pl.): 116 (1773), nom. superfl . – Type: Se- laginella spinosa P.Beauv., nom. superfl . [≡ Lycopodium selaginoi- des L. ≡ (L.) P.Beauv. ex Schrank & Mart. ≡ MATERIALS AND METHODS Selaginella spinulosa A.Braun ex Döll, nom. superfl .].

Our classifi cation is based on a phylogenetic analysis of Selaginella Selaginella subg. Selaginella – perennial, erect, with using DNA sequence data, combined with a morphological study of nonarticulate stems. Stems monostelic. at the base of shoot, the group ( Weststrand and Korall, 2016 , in this issue). Th e phyloge- from a hypocotular node. Rhizophores lacking. Vegetative leaves netic analysis included 223 species, represented by a total of 340 and sporophylls monomorphic, helically arranged. accessions. Choice of taxa was made to cover the taxonomical, morphological, and geographical variation seen in the family. Th e Species included— Selaginella selaginoides (circumboreal) and S. de- analyzed data set included DNA sequence data from both the plastid fl exa (). rbcL gene and the two single-copy nuclear regions pgiC and SQD1 . Voucher material included in the phylogenetic analysis was exam- Selaginella subg. Rupestrae Weststrand & Korall, nom. nov. – ined morphologically, with a focus on features possible to study by Selaginella subg. Tetragonostachys Jermy, Gaz. 13: 118 (1986), the naked eye or a stereomicroscope ( Weststrand and Korall, 2016 ). Th e nom. illeg. (replaced synonym) – S. sect. Homoeophyllae Spring in 2164 • AMERICAN JOURNAL OF BOTANY

TABLE 1. Morphological characteristics for the seven subgenera. Phyllotaxy Anisophylly? Subgenus Vegetative leaves Sporophylls Vegetative leaves Sporophylls Rhizophores Other features Selaginella Helical Helical No No No — Rupestrae Helical Tetrastichous No a No a Dorsal — Lepidophyllae Four rows Tetrastichous Yes No Dorsal Rosette-forming Gymnogynum Four rows Tetrastichous Yes b No Dorsal Articulations Exaltatae Four rows Tetrastichous Yes b No Dorsal Some articulate species; actino- or actino-plectostelic stems Ericetorum Decussate c or four rows d Tetrastichous No/Yes No Yes (position unclear) Megaspore pole; solenostelic rhizomes Stachygynandrum Four rows Tetrastichous Yes b No/Yes Ventral e —

a A few subg. Rupestrae species may have a tendency toward slightly dimorphic vegetative leaves and/or sporophylls. b At least on distal parts of . c Monomorphic vegetative leaves. d Dimorphic vegetative leaves. e Members of the sanguinolenta group have dorsal rhizophores.

Mart., Fl. Bras. 1(2): 118 (1840) – S. sect. Tetragonostachys Rothm. smaller leaves in the two upper (dorsal) rows. Sporophylls mono- Feddes Repert. Spec. Nov. Regni Veg. 54: 68 (1944), nom. illeg. – morphic in tetrastichous strobili. Bryodesma Soják, Preslia 64: 154 (1993, “1992”) – Lycopodioides subg. Tetragonostachys (Jermy) Tzvel., Novosti Sist. Vyssh. Rast. Species included— We include two species in subg. Lepidophyllae : S. 36: 25 (2004), nom. illeg. – Type: (L.) Spring (≡ lepidophylla (southwestern and Mexico) and S. novo- Lycopodium rupestre L.). leonensis Hieron. & Sadeb. (Mexico); a few other “resurrection Plants perennial, creeping, mat-forming, or sometimes erect. plants” may be included here. Note, however, that only resurrec- Stems monostelic, nonarticulate. Rhizophores dorsal. Vegetative tion plants with dorsal rhizophores belong in this subgenus. Th ose leaves monomorphic, helically arranged. Sporophylls monomor- with ventrally arising rhizophores belong in subg. Stachygynan- phic in tetrastichous strobili. drum. We do not know the position of rhizophores of, e.g., S. gyp- sophila A.R.Sm. & T.Reeves and S. ribae Valdespino (Smith and Species included—Ca. 50 species, mainly in , with a Reeves, 1984 ; Mickel et al., 2004 ). few species in , , and (Tryon, 1955; Jermy, 1990 ; Arrigo et al., 2013 ). Comments— Species in subg. Lepidophyllae were included in subg. Stachygynandrum sensu Jermy (1986) . In the classifi cation of Zhou Comments— Th e group includes xerophytic plants, where the distal and Zhang (2015) , this subgenus corresponds to sect. Lepidophyllae branches may or may not curl inward during drought. Subgenus (in a more inclusive subg. Ericetorum ). Rupestrae corresponds to subg. Tetragonostachys Jermy (but a name change is required, see discussion above), and to sect. Ho- Selaginella subg. Gymnogynum (P.Beauv.) Weststrand & moeophyllae (in a more inclusive subg. Ericetorum ) in the classifi - Korall, comb. nov. – Gymnogynum P.Beauv., Mag. Encycl. 9(5): 480 cation of Zhou and Zhang (2015) . (1804) – Lycopodium subg. Gymnogynum (P.Beauv.) Rchb., Consp. Regn. Veg.: 78 (1828) – Didiclis sect. Gymnogynum (P.Beauv.) Selaginella subg. Lepidophyllae (Li Bing Zhang & X.M.Zhou) Rothm., Feddes Repert. Spec. Nov. Regni Veg. 54: 70 (1944) – Type: Weststrand & Korall, stat. nov. – Selaginella sect. Lepidophyllae Li Gymnogynum domingense P.Beauv. [= Selaginella plumosa (L.) Bing Zhang & X.M.Zhou, Taxon 64: 1133 (2015) – Type: Selaginella C.Presl ≡ Lycopodium plumosum L.]. lepidophylla (Hook. & Grev.) Spring. Selaginella [unranked] Articulatae Spring in Mart., Fl. Bras. 1(2): Plants perennial with a rosetted habit. Stems monostelic, nonar- 118 (1840) – S. series Articulatae (Spring) Hieron. & Sadeb. in En- ticulate, curling inward in dry conditions forming a tight ball. Rhi- gler & Prantl, Nat. Pfl anzenfam. 1(4): 707 (1901) – Didiclis sect. zophores dorsal. Vegetative leaves dimorphic in four rows, the Articulata (Spring) Rothm., Feddes Repert. Spec. Nov. Regni Veg.

TABLE 2. A comparison of our classifi cation to two recent classifi cations. Our classifi cationJermy (1986) Zhou and Zhang (2015) Selaginella Selaginella Selaginella subg. Selaginella subg. Selaginella subg. Selaginella subg. Rupestrae subg. Tetragonostachys subg. Ericetorum sect. Homoeophyllae subg. Lepidophyllae subg. Stachygynandrum a subg. Ericetorum sect. Lepidophyllae subg. Ericetorum subg. Ericetorum and subg. Stachygynandrum a subg. Ericetorum sect. Lyallia subg. Gymnogynum subg. Stachygynandrum a subg. Ericetorum sect. Articulatae subg. Exaltatae subg. Stachygynandrum a subg. Ericetorum sect. Megalosporarum and subg. Ericetorum sect. Myosurus subg. Stachygynandrum subg. Stachygynandrum a and subg. Heterostachys a subg. Boreoselaginella , subg. Pulviniella , subg. Heterostachys (includes fi ve sections), and subg.Stachygynandrum (includes seven sections)

a Taxon not representing a monophyletic group. DECEMBER 2016 , VOLUME 103 • WESTSTRAND AND KORALL—SUBGENERIC CLASSIFICATION OF SELAGINELLA • 2165

54: 71 (1944) – Selaginella sect. Articulatae (Spring) Li Bing Zhang upper (dorsal) rows. Sporophylls monomorphic in tetrastichous & X.M.Zhou, Taxon 64: 1132 (2015) – Lectotype (designated by strobili. Strobili with a single (rarely two) basal megasporangium Rothmaler in Feddes Repert. Spec. Nov. Regni Veg. 54: 71, 1944): surrounded by enlarged sterile sporophylls. Didiclis sulcata (Desv. ex Poir.) Rothm. [≡ Selaginella sulcata (Desv. ex Poir.) Spring ex Mart.]. Species included—We include three species in subg. Exaltatae : S. Selaginella [unranked] Repentes A.Braun, Append. Pl. Nov. congoensis Alston and S. myosurus (both from Africa), and S. exal- Hort. Berol. 1857: 12 (1858), non Braun, ibid., p. 11 – Lectotype tata (Central and South America). Other possible members of the (designated by Zhou and Zhang in Taxon 64: 1132, 2015): Selagi- subgenus are: S. gigantea Steyerm. & A.R.Sm., S. anaclasta Alston nella hortensis Mett. [= S. kraussiana (Kunze) A.Braun]. ex Crabbe & Jermy, S. grallipes Alston, and S. versatilis A.R.Sm. Ar- Selaginella [unranked] Adscendentes A.Braun, Append. Pl. Nov. ticulations are found in the fi rst three species, but are missing in S. Hort. Berol. 1857: 12 (1858), non Braun, ibid., p. 11 – Lectotype versatilis ( Tardieu-Blot, 1964 ; Crabbe and Jermy, 1973 ; Steyermark (designated by Zhou and Zhang in Taxon 64: 1132, 2015): Selagi- and Smith, 1986 ; Smith, 1990 ). An actinostelic stem has previously nella galeottii Spring (= S. stellata Spring). been reported for S. gigantea (T- or X-shaped stele; Mickel and Selaginella [unranked] Caulescentes A.Braun, Append. Pl. Nov. Hellwig, 1969 ; Steyermark and Smith, 1986), and we have verifi ed a Hort. Berol. 1857: 12 (1858), non Braun, ibid., p. 11 – Type: Selagi- three-lobed actinostele in S. anaclasta (A. R. Smith, University of nella asperula Spring. California, Berkeley, personal observation) and in S. grallipes (S. Selaginella subser. Monostelicae Hieron. & Sadeb. in Engler & Weststrand and P. Korall, personal observation). Prantl, Nat. Pfl anzenfam. l(4): 708 (1901), non Hieron. & Sadeb. in Engler. & Prantl, Nat. Pfl anzenfam. l(4): 673, 704 (1901) – Lecto- Comments— Selaginella exaltata , with articulate stems, has tradi- type (designated here): Selaginella remotifolia Spring. tionally been included in the unranked Articulatae Spring, whereas Selaginella subser. Pleiostelicae Hieron. & Sadeb. in Engler. & S. congoensis and S. myosurus were placed in subg. Stachygynan- Prantl, Nat. Pfl anzenfam. l(4): 710. 1901, non Hieron. & Sadeb. in drum by Jermy (1986) . Besides the characters listed above, these Engler. & Prantl, Nat. Pfl anzenfam. l(4): 700, 707 (1901) – Lecto- plants commonly share a more or less scandent growth form, a fea- type (designated here): (Kunze) A.Braun. ture also seen in, e.g., S. willdenowii (Desv. ex Poir.) Baker. Both S. Plants perennial, with articulate stems. Stems mono- or bistelic, exaltata and S. myosurus also have megaspores with grid-like exo- in rare cases tri- or 4–5-stelic. Rhizophores dorsal. Vegetative leaves spore pattern in cross section (also seen in, e.g., species in subg. dimorphic (at least on distal parts of plant) in four rows, the smaller Gymnogynum ; Korall and Taylor, 2006 ). Th e species in subg. Exal- leaves in the two upper (dorsal) rows. Sporophylls monomorphic tatae were divided into two sections in the classifi cation of Zhou in tetrastichous strobili. Strobili with a single (rarely two) basal and Zhang (2015) : sect. Megalosporarum and sect. Myosurus (both megasporangium surrounded by enlarged sterile sporophylls. in a more inclusive subg. Ericetorum ). Megaspores with a grid-like exospore pattern in cross section. Selaginella subg. Ericetorum Jermy, Fern Gaz. 13: 117 (1986) – Species included— Th e subgenus includes an estimated 40 species S. [unranked] Tetrastichae A.Braun, Append. Pl. Nov. Hort. Berol. (based on the number of species that have traditionally been in- 1857: 11 (1858) – Type: (Labill.) Spring. cluded in series Articulatae ; Somers, 1982 ). Th e species are mainly Selaginella subser. Pleiostelicae Hieron. & Sadeb. in Engler & neotropical, with one species in Africa (S. kraussiana) and one spe- Prantl, Nat. Pfl anzenfam. 1(4): 707 (1901), non Hieron. & Sadeb. in cies ( S. remotifolia), or possibly a few species, in Asia (Somers, Engler & Prantl., Nat. Pfl anzenfam. 1(4): 700, 710 (1901) – Didiclis 1982 ; Moran and Smith, 2001 ). sect. Lyallia Rothm., Feddes Repert. Spec. Nov. Regni Veg. 54: 70 (1944) – Selaginella sect. Lyallia (Rothm.) Li Bing Zhang & Comments— Selaginella subser. Monostelicae Hieron. & Sadeb. and X.M.Zhou, Taxon 64: 1133 (2015) – Type: Selaginella lyallii (Hook. S. subser. Pleiostelicae Hieron. & Sadeb. are lectotypifi ed here. Both & Grev.) Spring. taxa were listed with types by Zhou and Zhang (2015) , but as no Plants annual or perennial, erect, with nonarticulate stems. Rhi- previous typifi cations have been found, lectotypifi cations are re- zomes (when present) solenostelic with rhizophores. Erect branches quired here. commonly polystelic (perennials). Vegetative leaves monomor- Subgenus Gymnogynum is most easily confused with subg. Exal- phic, decussately arranged, at least on proximal parts of plants. tatae (below), but diff ers in stelar arrangement. Also, species in subg. Larger species anisophyllous in distal parts of plants. Dimorphic Exaltatae are commonly scandent and oft en lack articulations. Spe- vegetative leaves in four rows, the two upper (dorsal) rows with cies in subg. Gymnogynum were included in subg. Stachygynandrum smaller leaves. Sporophylls monomorphic in tetrastichous strobili. by Jermy (1986) . Th e subgenus corresponds to sect. Articulatae Megaspores with wing-like laesurae and high porosity at the proxi- (Spring) Li Bing Zhang & X.M.Zhou (in a more inclusive subg. Erice- mal pole, forming a “complex mass” in some species. torum ) in the classifi cation of Zhou and Zhang (2015) . Species included— Selaginella uliginosa and S. gracillima (both from Selaginella subg. Exaltatae Weststrand & Korall, subg. nov. – S. ), S. pygmaea (South Africa and, depending on species de- sect. Megalosporarum Li Bing Zhang & X.M.Zhou, Taxon 64: 1133 limitations, possibly Australia, see Schulz et al., 2013, for a discus- (2015) – Type: Selaginella exaltata (Kunze) Spring. sion), S. lyallii , S. pectinata Spring, and S. moratii W.Hagemann & Selaginella sect. Myosurus Li Bing Zhang & X.M.Zhou, Taxon Rauh (last three from Madagascar). Selaginella pectinata was in 64: 1133 (2015) – Type: Selaginella myosurus (Sw.) Alston. earlier publications (Stefanović et al., 1997; Korall and Kenrick, Plants perennial. Stems actino- or actino-plectostelic, articulate 2002 ; Zhou et al., 2015c ) referred to as S. polymorpha Badré (see or not. Rhizophores dorsal. Vegetative leaves dimorphic (at least on Smith et al., 2016 , for a discussion). According to Schulz et al. distal parts of plants) in four rows, the smaller leaves in the two (2013) , S. royenii Alston from New Guinea is also a member of this 2166 • AMERICAN JOURNAL OF BOTANY

subgenus. Depending on the taxonomy of the Madagascan species Circinatae (Hook. & Grev.) Li Bing Zhang & X.M.Zhou, Taxon 64: complex, the species number may increase. 1136 (2015) – S. [unranked] Rosulatae A.Braun, Append. Pl. Nov. Hort. Berol. 1857: 11 (1858) – S. ser. Rosulatae (A.Braun) Baker, J. Comments— Selaginella [unranked] Tetrastichae A.Braun and S. Bot. 21: 4 (1883) – Lycopodioides sect. Rosulatae (A.Braun) Tzvel., subser. Pleiostelicae Hieron. & Sadeb. in Engler & Prantl (1901: 707, Novosti Sist. Vyssh. Rast. 36: 25 (2004) – Type: Selaginella involvens non Hieron. & Sadeb., ibid., 1901: 700, 710) were lectotypifi ed by (Sw.) Spring (≡ Lycopodium involvens Sw.). Zhou and Zhang (2015: 1133). Th e wide circumscription of Selagi- Lycopodium [unranked] Tetragonostachya Hook. & Grev., Bot. nella subg. Ericetorum by Zhou and Zhang (2015) includes the type Misc. 2: 382 (1831) – Lycopodium [unranked] Planifolia Hook. & of the earlier published Lycopodium subg. Gymnogynum (P.Beauv.) Grev., Bot. Misc. 2: 382 (1831) – Selaginella [unranked] Planifoliae Rchb. Th e name as it was used by Zhou and Zhang (2015) is there- (Hook. & Grev.) Spring in Mart., Fl, Bras. 1(2): 118 (1840) – Selagi- fore incorrect. nella [unranked] Tetragonostachyae (Hook. & Grev.) Spring, Mém. Th e unique megaspore surface at and around the proximal pole Acad. Roy. Sci. Belgique 24: 53 (1849) – S. sect. Tetragonostachyae (see, e.g., Korall and Taylor, 2006 ; Stefanović et al., 1997 ; Schulz (Hook. & Grev.) Hieron. & Sadeb. in Engler & Prantl, Nat. Pfl an- et al., 2013 ) was not recognized as an apomorphy diagnostic for the zenfam. 1(4): 669 (1901) – S. sect. Tetragonostachyae (Hook. & subgenus by Jermy (1986). Whether the rhizophores originating Grev.) Rothm., Feddes Repert. Spec. Nov. Regni Veg. 54: 68 (1944) from the rhizome should be considered to arise in a ventral or dor- (“ Tetragonostachya ”) – Type: Lycopodium tetragonostachyum sal position in relation to branch dichotomies is unclear. Jermy Wall. ex. Hook. & Grev. [≡ Selaginella tetragonostachya (Wall. ex (1986) included only the three Australian/South African species in Hook. & Grev.) Spring]. subg. Ericetorum , but based on our phylogenetic analysis, we also Selaginella [unranked] Platystachya Hook. & Grev., Bot. Misc. 2: include three Madagascan taxa. Subgenus Ericetorum corresponds 400 (1831) – S. [unranked] Platystachyae (Hook. & Grev.) Spring, to sect. Lyallia (in a more inclusive subg. Ericetorum ) in the classi- Mém. Acad. Roy. Sci. Belgique 24: 54 (1849) – Lectotype (desig- fi cation of Zhou and Zhang (2015) . nated by Zhou and Zhang in Taxon 64: 1134, 2015): Selaginella chrysocaulos (Hook. & Grev.) Spring. Selaginella subg. Stachygynandrum (P.Beauv. ex Mirb.) Baker, Selaginella sect. Heterophyllae Spring in Mart., Fl. Bras. 1(2): 118 J. Bot. 21: 3 (1883) – Stachygynandrum P.Beauv. ex Mirb. in Lam. & (1840) – S. [unranked] Enodes Spring in Mart., Fl. Bras. 1(2): 118 Mirb., Hist. Nat. Vég. 3: 477 (1803) – Lycopodium subg. Stachygyn- (1840) – S. [unranked] Adscendentes A.Braun, Append. Pl. Nov. andrum (P.Beauv. ex Mirb.) Spreng., Anleit. Kenntn. Gew., ed. 2, Hort. Berol. 1857: 11 (1858), non Braun, ibid., p. 12 – S. [unranked] 2(1): 109 (1817) – Lycopodium [unranked] Stachygynandrum Persistentes A.Braun, Append. Pl. Nov. Hort. Berol. 1857: 11 (1858) – (P.Beauv. ex Mirb.) Hook. & Grev., Bot. Misc. 2: 380 (1831) – Lyco- S. sect. Dichotropae A.Braun, Append. Pl. Nov. Hort. Berol. 1857: podium [unranked] Stachygynandrum (P.Beauv. ex Mirb.) Kunze, 11 (1858), nom. illeg. – S. sect. Pleiomacrosporangiatae Hieron. & Linnaea 9: 8 (1834) (“Stachygynandra ”) – Selaginella sect. Stachygy- Sadeb. in Engler & Prantl, Nat. Pfl anzenfam. 1(4): 673 (1901) – S. nandrum (P.Beauv. ex Mirb.) T.Moore, Index Fil.: cxxviii (1857) ser. Monostelicae Hieron. & Sadeb. in Engler & Prantl, Nat. Pfl an- (“ Stachygynandrium “) – Selaginella subg. Heterophyllum Hieron. & zenfam. 1(4): 673 (1901), non Hieron & Sadeb. in Engler & Prantl, Sadeb. in Engler and Prantl, Nat. Pfl anzenfam. 1(4): 673 (1901) – Nat. Pfl anzenfam. 1(4): 704, 708 (1901) – Lectotype (designated by Didiclis subg. Stachygynandrum (P.Beauv. ex Mirb.) Rothm., Fed- Zhou and Zhang in Taxon 64: 1136, 1137, 2015): Selaginella fl ex- des Repert. Spec. Nov. Regni Veg. 54: 70 (1944) – Didiclis subg. uosa Spring. Heterophyllum (Hieron. & Sadeb.) Rothm., Feddes Repert. Spec. Selaginella [unranked] Continuae Spring, Mém. Acad. Roy. Sci. Nov. Regni Veg. 54: 70 (1944) – Lycopodioides sect. Stachygynan- Belgique 24: 53 (1849) – S. [unranked] Pusillae Spring, Mém. Acad. drum (P.Beauv. ex Mirb.) Tzvel., Novosti Sist. Vyssh. Rast. 36: 25 Roy. Sci. Belgique 24: 53 (1849) – S. ser. Decumbentes Baker, J. Bot. (2004) – Type: Selaginella fl abellata (L.) Spring (≡ Lycopodium fl a- 21: 3 (1883) – S. ser. Continuae Hieron. & Sadeb. in Engler & Prantl, bellatum L.). Nat. Pfl anzenfam. 1(4): 704 (1901) – Lectotype (designated by Lycopodioides Boehm. in Ludwig, Def. Gen. Pl. ed. 3: 485 (1760), Zhou and Zhang in Taxon 64: 1137, 2015): Selaginella microphylla nom. rej. – Trispermium Hill, Gener. Nat. Hist., ed. 2, 2 (Hist. Pl.): (Kunth) Spring. 112 (1773), nom. superfl . – Selaginella [unranked] Complanatae Selaginella [unranked] Proceres Spring, Mém. Acad. Roy. Sci. Spring, Mém. Acad. Roy. Sci. Belgique 24: 53 (1849) – Type: Lyco- Belgique 24: 53 (1849) – S. sect. Proceres (Spring) Li Bing Zhang & podioides denticulatum (L.) Kuntze [≡ (L.) X.M.Zhou, Taxon 64: 1137 (2015) – Lectotype (designated by Zhou Spring]. and Zhang in Taxon 64: 1137, 2015): Selaginella oaxacana Spring. Didiclis P.Beauv. ex Mirb. in Lam. & Mirb., Hist. Nat. Vég. 3: 477 Selaginella [unranked] Repentes A.Braun, Append. Pl. Nov. (1803) – Type: Didiclis ornithopodioides (L.) P.Beauv. ex J.St.-Hil. Hort. Berol. 1857: 11 (1858), non Braun, ibid., p. 12 – Lectotype [≡ Selaginella ornithopodioides (L.) Spring]. (designated by Zhou and Zhang in Taxon 64: 1134, 2015): Selagi- Diplostachyum P.Beauv., Mag. Encycl. 9(5): 481 (“Diplosta- nella helvetica (L.) Spring. chium ”) (1804) – Lycopodium subg. Diplostachyum (P.Beauv.) Selaginella [unranked] Redivivae A.Braun, Append. Pl. Nov. Rchb., Consp. Regn. Veg.: 78 (1828) – Selaginella sect. Diplo- Hort. Berol. 1857: 11 (1858) – Lectotype (designated by Zhou and stachyum (P.Beauv.) T.Moore, Index Fil.: cxxviii (1857) – Lycopodi- Zhang in Taxon 64: 1136, 2015): Selaginella ciliata (Willd.) A. oides sect. Diplostachyum (P.Beauv.) Rothm., Feddes Repert. Spec. Braun [= S. novae-hollandiae (Sw.) Spring]. Nov. Regni Veg. 54: 69 (1944) – Type: Diplostachyum tenellum Selaginella [unranked] Erectae A.Braun, Append. Pl. Nov. Hort. P.Beauv. (≡ Selaginella tenella (P.Beauv.) Spring). Berol. 1857: 11 (1858) – S. ser. Sarmentosae Baker, J. Bot. 21: 4 Lycopodium [unranked] Circinatae Hook. & Grev., Bot. Misc. 2: (1883) – Type: Selaginella inaequalifolia (Hook. & Grev.) Spring. 380 (1831) (“Circinata ”) – Selaginella [unranked] Circinatae Selaginella [unranked] Scandentes A.Braun, Append. Pl. Nov. (Hook. & Grev.) Spring in Mart., Fl, Bras. 1(2): 118 (1840) – S. sect. Hort. Berol. 1857: 11 (1858) – S. ser. Scandentes (A.Braun) Baker, J. DECEMBER 2016 , VOLUME 103 • WESTSTRAND AND KORALL—SUBGENERIC CLASSIFICATION OF SELAGINELLA • 2167

Bot. 21: 4 (1883) – Lectotype (designated by Zhou and Zhang in Spec. Nov. Regni Veg. 54: 70 (1944) (“Oligomacrosporangiata ”) – Taxon 64: 1135, 2015): Selaginella laevigata (Willd.) Spring [= S. Type: Selaginella fi ssidentoides (Hook. & Grev.) Spring. willdenowii (Desv. ex Poir.) Baker]. Hypopterygiopsis Sakurai, Bot. Mag. (Tokyo) 57: 255 (1943) – Selaginella [unranked] Caulescentes A.Braun, Append. Pl. Nov. Type: Hypopterygiopsis reptans Sakurai (≡ Selaginella sakuraii Hort. Berol. 1857: 11 (1858), non Braun, ibid., p. 12 – S. ser. Caules- H.A.Mill.). centes (A.Braun) Baker, J. Bot. 21: 4 (1883) – Type: Selaginella Selaginella subg. Pulviniella Li Bing Zhang & X.M.Zhou, Taxon 64: caulescens (Wall. ex Hook. & Grev.) Spring [= S. involvens (Sw.) 1133 (2015) – Type: Selaginella pulvinata (Hook. & Grev.) Maxim. Spring]. Selaginella sect. Auriculatae Li Bing Zhang & X.M.Zhou, Taxon Selaginella [unranked] Pronae A.Braun, Append. Pl. Nov. 64: 1134 (2015) – Type: Selaginella douglasii (Hook. & Grev.) Hort. Berol. 1857: 12 (1858) – Lectotype (designated by Zhou Spring. and Zhang in Taxon 64: 1135, 2015): Selaginella ciliaris (Retz.) Selaginella sect. Austroamericanae Li Bing Zhang & X.M.Zhou, Spring. Taxon 64: 1136 (2015) – Type: Selaginella hartwegiana Spring. Selaginella [unranked] Resupinatae A.Braun, Append. Pl. Selaginella sect. Pallescentes Li Bing Zhang & X.M.Zhou, Taxon Nov. Hort. Berol. 1857: 12 (1858) – Lectotype (designated by 64: 1137 (2015) – Type: Selaginella pallescens (C.Presl) Spring. Zhou and Zhang in Taxon 64: 1137, 2015): Selaginella steno- Plants perennial, creeping to erect, sometimes long, scandent, phylla A.Braun. with nonarticulate stems. Stems commonly monostelic, rarely Selaginella ser. Ascendentes Baker, J. Bot. 21: 3 (1883) – S. sect. tristelic or actinostelic. Rhizophores mostly ventral (proximally or Ascendentes (Baker) Li Bing Zhang & X.M.Zhou, Taxon 64: 1136 throughout the plant), dorsal in a few species (S. sanguinolenta , S. (2015) – S. ser. Radicantes Warb., Monsunia 1: 102 (1900) – Lecto- nummularifolia Ching, and possibly close relatives). Vegetative type (designated by Zhou and Zhang in Taxon 64: 1136, 2015): Se- leaves dimorphic (at least on distal parts of plant) in four rows, the laginella alopecuroides Baker. smaller leaves in the two upper (dorsal) rows. Sporophylls mono- Selaginella subg. Homostachys Baker, J. Bot. 21: 4 (1883) – S. morphic in tetrastichous strobili, or dimorphic in resupinate or sect. Homostachys (Baker) Li Bing Zhang & X.M.Zhou, Taxon 64: nonresupinate strobili (i.e., with the smaller sporophylls in the 1134 (2015) – Lectotype (designated by Zhou and Zhang in Taxon same plane as the larger vegetative leaves or vice versa). 64: 1134, 2015): Selaginella pallidissima Spring. Selaginella subg. Heterostachys Baker, J. Bot., 21: 4 (1883) – S. Species included— Ca. 600 species, with greatest species diversity in sect. Heterostachys Li Bing Zhang & X.M.Zhou, Taxon 64: 1134 the tropics, but also in the subtropics and temperate areas of the (2015) – Type: Selaginella heterostachys Baker. world. Selaginella subg. Boreoselaginella Warb., Monsunia 1: 100 (1900) – Lectotype (designated by Zhou and Zhang in Taxon 64: 1129, Comments— Lycopodioides Boehm. was lectotypifi ed by Rothmaler 2015): Selaginella borealis (Kaulf.) Spring [= S. sanguinolenta (L.) (1944 : 69). Didiclis sect. Oligomacrosporangiatae (Hieron. & Spring]. Sadeb.) Rothm. was lectotypifi ed by Rothmaler (1944 : 70). Selagi- Selaginella subser. Plagiophyllae Warb., Monsunia 1: 103 (1900) – nella subg. Heterostachys Baker and S. subg. Stachygynandrum S. sect. Plagiophyllae (Warb.) Li Bing Zhang & X.M.Zhou, Taxon (P.Beauv. ex Mirb.) Baker were lectotypifi ed by Jermy (1986 : 118). 64: 1137 (2015) – Lectotype (designated by Zhou and Zhang in Selaginella [unranked] Complanatae Spring was lectotypifi ed by Taxon 64: 1137, 2015): Selaginella biformis A.Braun ex Kuhn. Zhou and Zhang (2015: 1134). Lycopodium [unranked] Planifolia Selaginella subser. Pleurophyllae Warb., Monsunia 1: 106 (1900) – Hook. & Grev., Selaginella [unranked] Planifoliae (Hook. & Grev.) Lectotype (designated by Zhou and Zhang in Taxon 64: 1135, Spring, S. ser. Sarmentosae Baker, and S. subser. Monostelicae Hi- 2015): (Desv. ex Poir.) Baker. eron. & Sadeb. in Engler & Prantl (1901: 704, non Hieron & Sadeb., Selaginella ser. Bisulcatae Warb., Monsunia 1: 108 (1900) – ibid., 1901: 673, 708) were lectotypifi ed by Zhou and Zhang (2015 : Type: Selaginella bisulcata Spring. 1135). Lycopodium [unranked] Circinatae Hook. & Grev., Selagi- Selaginella ser. Pronifl orae Warb., Monsunia 1: 108 (1900) – nella [unranked] Circinatae (Hook. & Grev.) Spring, S. sect. Circi- Type: Selaginella pronifl ora (Lam.) Baker. natae (Hook. & Grev.) Li Bing Zhang & X.M.Zhou, and S. subg. Selaginella ser. Brachystachyae Warb., Monsunia 1: 110 (1900) – Heterophyllum Hieron. & Sadeb. were lectotypifi ed by Zhou and Type: Selaginella brachystachya (Hook. & Grev.) Spring. Zhang (2015 : 1136). Selaginella ser. Suberosae Warb., Monsunia 1: 110 (1900) – Type: Two species, S. sanguinolenta and S. nummularifolia, are tenta- Selaginella suberosa Spring. tively placed in this subgenus. Th e two species are strongly sup- Selaginella sect. Pleiostelicae Hieron. & Sadeb. in Engler & ported as a monophyletic group (the sanguinolenta group), but the Prantl, Nat. Pfl anzenfam. 1(4): 700 (1901), non Hieron & Sadeb. in phylogenetic analyses are inconclusive with respect to the clade’s Engler & Prantl, Nat. Pfl anzenfam. 1(4): 707, 710 (1901) – Lycopo- position. Th e morphology of the species suggests a close relation- dioides sect. Pleiostelica (Hieron. & Sadeb.) Rothm., Feddes Repert. ship with subg. Stachygynandrum , one of two topologies found by Spec. Nov. Regni. Veg. 54: 69 (1944) (“Pleiostele ”) – Lectotype (des- the analyses (see Weststrand and Korall [2016] in this issue for a ignated by Rothmaler in Feddes Repert. Spec. Nov. Regni Veg. 54: discussion). As compared with subg. Stachygynandrum sensu 69 (1944): (Desv. ex Poir.) Spring. Jermy (1986), subg. Stachygynandrum as circumscribed here also Selaginella sect. Oligomacrosporangiatae Hieron. & Sadeb. in includes species with resupinate strobili that Jermy (1986) placed in Engler & Prantl, Nat. Pfl anzenfam. 1(4): 704 (1901) – Selaginella subg. Heterostachys Baker; however, it excludes species now in- subser. Monostelicae Hieron. & Sadeb. in Engler & Prantl, Nat. cluded in subgenera Lepidophyllae , Gymnogynum , Exaltatae , and Pfl anzenfam. 1(4): 704 (1901), non Hieron & Sadeb. in Engler & Ericetorum . Th e subgenus corresponds to the four subgenera Prantl, Nat. Pfl anzenfam. 1(4): 673, 708 (1901) – Didiclis sect. Stachygynandrum , Heterostachys , Pulviniella , and Boreoselaginella Oligomacrosporangiatae (Hieron. & Sadeb.) Rothm., Feddes Repert. in the classifi cation of Zhou and Zhang (2015) . 2168 • AMERICAN JOURNAL OF BOTANY

KEY TO THE SUBGENERA OF SELAGINELLA Baker , J. G. 1883 . A synopsis of the genus Selaginella. Journal of Botany 21 : 1 – 5, 42–46, 80–84, 97–100, 141–145, 210–213, 240–244 . 1. Vegetative leaves helically arranged and monomorphic; sporophylls Baker , J. G. 1885 . A synopsis of the genus Selaginella. Journal of Botany 23 : helically arranged or in tetrastichous strobili …………………….2 19 – 25, 45–48, 116–122, 154–157, 176–180, 248–252, 292–302 . 1. Vegetative leaves (at least in distal parts of plants) in four rows or Bower , F. O. 1908 . Th e origin of a land fl ora. Macmillan and Co., London, UK. Braun , A. 1858 . Selaginellae hortenses. In A. Braun [ed.], Appendix plantarum decussately arranged; sporophylls in tetrastichous strobili (shoots novarum et minus cognitarum in Horto regio botanico Berolinensi coluntur most oft en anisophyllous with vegetative leaves in four rows, ex- 1857, 11–24. C. Feisteri, Berlin, Germany. cept for a few Ericetorum species)…………………………....….3 Brause , G. 1921 . Bearbeitung der von C. Ledermann von der Sepik-(Kaiserin- 2. Sporophylls helically arranged; rhizophores lacking…………… Augusta-)Fluß-Expedition 1912 bis 1913 und von anderen Sammlern aus …………………………………………………...subg. Selaginella dem Papuagebiete früher mitgebrachten Pteridophyten, nebst Übersicht 2. Sporophylls in tetrastichous strobili; rhizophores dorsal über alle bis jetzt aus dem Papuagebiet bekannt gewordenen Arten derselben. …………………………………..………………. subg. Rupestrae In A. Engler [ed.], Botanische Jahrbücher für Systematik, Pfl anzengeschichte 3. Stems articulate………………………………………………….4 und Pfl anzengeographie, vol. 56, 223–244. W. Engelmann, Leipzig, Germany. 3. Stems nonarticulate…..………………………………………….5 Brizicky , G. K. 1969 . Subgeneric and sectional names: Th eir starting points and 4. Stems actino- or actino-plectostelic; plant commonly scandent early sources. Taxon 18 : 643 – 660 . Crabbe , J. A. , and A. C. Jermy . 1973 . Seven new species of Selaginella from …………………………… ………………………subg. Exaltatae tropical South America. American Fern Journal 63 : 135 – 144 . 4. Stems mono-, bi-, tri-, or 4–5-stelic; plant not scandent…… Dahlen , M. A. 1988 . Taxonomy of Selaginella : A study of characters, tech- ...……………………………………………. subg. Gymnogynum niques, and classifi cation in the Hong Kong species. Botanical Journal of the 5. Rhizophores dorsal… …… …… …… …… ……………………6 Linnean Society 98 : 277 – 302 . 5. Rhizophores ventral and/or from rhizomes (if present)…....…..8 Gardner , R. O. 1997 . A concise account of Selaginella in Fiji. 6. Rosetted habit……….………………..……...subg. Lepidophyllae Journal of Botany 35 : 269 – 281 . 6. Not rosetted habit…………………………………….………….7 Harvey-Gibson , R. J. 1894 . Contributions towards a knowledge of the anatomy 7. Stems actino- or actino-plectostelic; plant commonly scandent, of the genus Selaginella , Spr. I. Th e stem. Annals of Botany 8 : 133 – 206 . not xerophytic; megaspores reticulate……..…….subg. Exaltatae Hellwig , R. L. 1969 . of the heterophyllous Selaginellae of Mexico and 7. Stems monostelic; plant creeping, xerophytic; megaspores with . Annals of the Missouri Botanical Garden 56 : 444 – 464 . solitary protrusions……………………………………………… Hieronymus , G. , and R. Sadebeck . 1901 . Selaginellaceae . In A. Engler and K. Prantl [eds.], Die natürlichen Pfl anzenfamilien, vol. 1, part 4, 621–716. W. …………….the sanguinolenta group in subg. Stachygynandrum Engelmann, Leipzig, Germany. 8. Rhizomes (if present) solenostelic; megaspores with wing-like Horner , H. T. , and H. J. Arnott . 1963 . Sporangial arrangement in North laesurae and high porosity at the proximal pole, forming a “complex American species of Selaginella. Botanical Gazette 124 : 371 – 383 . mass” in some species; rhizophores from rhizome (if present) or Jermy , A. C. 1986 . Subgeneric names in Selaginella. Fern Gazette 1 3 : at base of upright stems; shoots iso- and/or anisophyllous 117 – 118 . ……………………………………….………….subg. Ericetorum Jermy , A. C. 1990 . Selaginellaceae . In K. Kubitzki [ed.], Th e families and genera 8. Rhizomes (if present) protostelic; megaspores variously orna- of vascular plants, vol. 1, K. U. Kramer and P. S. Green [eds.], mented, not as above; rhizophores ventral or at base of stems; and , 39–45. Springer, Berlin, Germany. shoots ± anisophyllous………………….subg. Stachygynandrum Jermy , A. C. , and J. S. Holmes . 1998 . Selaginellaceae . In , vol. 48, , gymnosperms and allied groups, 85–95. Australian Biological Resources Study/CSIRO Publishing, Canberra/Collingwood, Australia. ACKNOWLEDGEMENTS Karrfalt , E. E. 1981 . Th e comparative and developmental morphology of the We thank M. Th ulin and M. Lidén for help with nomenclature and root system of Selaginella selaginoides (L.) Link. American Journal of Botany A. Smith for fruitful discussions on Selaginella . We also thank M. 68 : 244 – 253 . Lidén, M. Th ollesson, M. Th ulin, and the reviewers for valuable Korall , P. , and P. Kenrick . 2002 . Phylogenetic relationships in Selaginellaceae based on rbcL sequences. American Journal of Botany 89 : 506 – 517 . comments on earlier versions of the manuscript. Th is work was Korall , P. , and P. Kenrick . 2004 . Th e phylogenetic history of Selaginellaceae supported by the Swedish Research Council for Environment, based on DNA sequences from the plastid and nucleus: Extreme substitu- Agricultural Sciences and Spatial Planning (“Formas”; 2006-429 tion rates and rate heterogeneity. Molecular Phylogenetics and Evolution 31 : and 2010-585 to P.K.) and by Anna Maria Lundins stipendiefond, 852 – 864 . Helge Ax:son Johnsons stift else, Sernanders stift else, and Stift elsen Korall , P. , P. Kenrick , and J. P. Th errien . 1999 . Phylogeny of Selaginellaceae: Extensus (to S.W.). 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